A person’s chronotype – their innate tendency to sleep at a particular time during a 24-hour period – is based on genetically determined circadian rhythms. Disruption of a person’s chronotype schedule can influence mood, productivity, and disease risk. A recent study shows that having a late chronotype increases a person’s risk of coronary artery calcification, a marker of atherosclerosis.

Researchers assessed the extent of coronary artery calcification in 771 middle-aged adults using computer tomography (CT). They monitored the participants' physical activity levels and asked them to identify their chronotype: extreme morning, moderate morning, intermediate, moderate evening, or extreme evening.

They found that extreme evening chronotypes were 90 percent more likely to have coronary artery calcification than extreme morning types. In addition, the later a participant’s chronotype, the greater their coronary artery calcification, roughly doubling from 22 percent for extreme morning types to 41 percent for extreme evening types.

These findings suggest that chronotype influences a person’s risk for atherosclerosis. They also align with other research showing that people with evening chronotypes are at greater risk for cardiovascular disease and premature death than morning types. Learn more about chronotypes and their effects on human health in this clip featuring Dr. Matthew Walker.

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